Confinement Effects of Metal-Organic Framework on the Formation of Charge-Transfer Tetrathiafulvalene Dimers.

Three transition metal coordination polymers (CPs) based on the redox-active dimethylthio-tetrathiafulvalene-bicarboxylate (L) and 1,3-bi(4-pyridyl)propane (bpp) ligands, formulated as [MnL(bpp)] _n (1), [CdL(bpp)] _n (2), and [Cd ₂ L(bpp) ₂ (H ₂ O)(C ₂ O ₄ ) _0.5 ] _n ·n(ClO ₄ )·n(H ₂ O) (3), are crystallographically characterized. Complexes 1 and 2 are isostructural 2-D polymers, and 3 features an unusual 3-D metal-organic framework (MOF). The 3-D MOF is constructed from tetranuclear cluster nodes built through the μ ₂ -O bridge of the TTF ligand, which is first found for TTF coordination polymers. It is found that the channel generated by the 3-D MOF exerts a confinement effect on the formation of TTF dimers. The TTF dimers show strong intradimer interaction with partial electron transfer or charge transfer, and hence, the Cd compound 3 has relatively good photocurrent response property in comparison with that of 2-D Cd compound 2.